Expression of the transferrin receptor on murine peritoneal macrophages is modulated by in vitro treatment with interferon gamma

The expression of transferrin receptors on murine peritoneal macrophages has been shown to be down regulated during functional activation in vivo. This observation suggested that the level of transferrin receptor expression varies in response to discrete extracellular signals known to induce macrophage activation. We have tested this concept directly and have shown that decreased transferrin receptor expression can be reproduced in vitro by treatment of inflammatory macrophages with preparations of interferon gamma derived from a T cell hybridoma supernatant. The ability of this agent to down regulate the expression of the transferrin receptor exhibited dose and time dependencies similar to those required for development of other macrophage functions in vitro. The addition of LPS produced no further decrease in receptor expression. Furthermore, murine gamma interferon, produced by recombinant DNA technology also caused a downshift in transferrin receptor expression at doses similar to those which have been shown previously to induce activation. The changes in receptor activity were the result of altered numbers of binding sites and the receptor:ligand affinity remained unaffected. These results indicate that altered expression of the transferrin receptor is one element of the pleiotypic change which macrophages undergo in response to IFN gamma. This system may, therefore, provide a useful model in which to study the biochemical basis of IFN gamma action in mononuclear phagocytes.     

Social Spacing in Small Mammals: Patterns of Individual Variation

The pattern of social spacing in small mammals differs fromthat observed in many other vertebrates. Small mammals frequentlyhave non-exclusive territories and tolerate a large amount ofoverlap with other conspecifics. The determinant factors ofhome range or territory size in small mammals are not knownfor most species. We carried out a study of the determinantfactors of home range size in a model small mammal, the easternchipmunk, Tamias striatus. The population was studied for fiveyears. The effect of experimental perturbations on food supplyand population density offered strong evidence that the meanhome range size in the population was determined by resourceabundance. Changes in population density had little or no measurableeffect. We noted that even when mean home range size decreasedsignificantly in response to an increase in available food,a great deal of variability in individual home range sizes remained.We hypothesized that this pattern of variation among individualswas also resource related; large home ranges would be locatedin areas of low resource density and small home ranges wouldbe located in areas of high resource density. Our data to datedo not offer support for this hypothesis; however our researchhas shown that the data needed to convincingly reject the nullhypothesis are very complex. We discuss the evidence requiredto study patterns of individual variation, and how models ofoptimal territory size may be useful. Research that examinespatterns of individual variation are few in number, yet studiesof individual variation will ultimately provide the best insightson the dynamics of evolutionary ecology.     

Cardiovascular and Other Physiological Correlates of Hibernation in Aquatic and Terrestrial Turtles

Recent research has provided new insight into the physiologyof hibernation in freshwater, marine, and terrestrial turtles.In this paper I review what is known about the mechanisms thatpermit the hearts of these turtles to withstand several monthsof hypoxia or anoxia. I also report new research that indicatesthat a terrestrial turtle, unlike freshwater and marine species,does not experience hypoxia in its winter burrow and thus doesnot rely on glycolysis to supply ATP, at least under moderatewinter conditions.     

Aerosol anesthesia increases hypercapnic ventilation and breathlessness in laryngectomized humans

The effect of local anesthetic aerosol inhalation on the ventilatory response and the sensation of breathlessness to CO2 rebreathing was studied in seven healthy male subjects with permanent tracheal stomas after laryngectomy for carcinoma. Inhalation of bupivacaine aerosol sufficient to abolish the cough reflex to mechanical probing below the carina increased the ventilatory response to CO2 in six of seven subjects compared with saline control. This was achieved by an increase in both respiratory frequency (f) and tidal volume (VT) in four subjects, f in one subject, and VT in one subject. All subjects reported that they were more breathless on rebreathing after bupivacaine aerosol. The six subjects who recorded breathlessness with a visual analog scale (VAS) indicated its onset at a lower minute ventilation (VE) and gave higher VAS scores for equivalent levels of VE after threshold. We conclude that the enhanced CO2 sensitivity and breathlessness on rebreathing after airway anesthesia results from altered lower airway receptor discharge.     

THE PSYCHOPHYSICAL RELATIONSHIP BETWEEN COLOR AND SALT CONCENTRATIONS IN CHICKEN FLAVORED BROTHS

Taste panelists evaluated the effect of color on salt perception in chicken flavored samples using magnitude estimation. Samples were colored to simulate commercial chicken broth. Five color intensities were added to 5 NaCl concentrations ranging from 0.34 to 0.66% (w/v). Color had no influence on salt perception. Panelists were able to perceive color differences among samples (P <0.001) and these were correlated with the objective color function cot⁻¹ (a/b) calculated from the L,a,b values obtained from the Gardner XL-23. Overall flavor preference was evaluated by a taste panel using the technique of magnitude estimation. NaCl concentrations ranged from 0.52 to 0.80% (w/v). Overall flavor preference was unaffected by color. A reduction in NaCl concentration from 0.80% (w/v) to 0.52% (a 35% reduction) did not alter flavor preference. A 50 member consumer panel using a paired comparison test found no difference in flavor preference between an uncolored sample containing 0.80% (w/v) NaCl and a colored sample containing 0.72% (w/v) NaCl.     

DISSIMILARITIES IN COGNITION OF FLAVOUR TERMS RELATED TO VARIOUS SENSORY LABORATORIES IN A MULTIVARIATE STUDY

A study of dissimilarities in cognitive perception of 20 common flavor terms was carried out by the Sensory Group of Norway. An average cognitive pattern of the flavor terms was revealed from multidimensional scaling (MDS) and cluster analysis (CLU). In general, small but interesting deviations between different sensory laboratories working with various food products were found by a multivariate pattern recognition technique based on principal component analysis (PCA). Suggestions for finding general reference standards for flavor terms are discussed.     

A comparison of local recurrence and resection margins for stage I primary cutaneous malignant melanomas

A retrospective review of 552 patients with clinical stage I primary cutaneous malignant melanomas was undertaken comparing margins of resection and local recurrence between 1966 and 1981. The overall local recurrence rate was 8 per 552 (1.45 percent). We observed no instances of local recurrence in lesions less than 1.40 mm thick with resection margins of at least 1 cm. A comparison of resection margins greater than 2 cm versus less than 2 cm for lesions less than 1.00 mm thick showed no difference at the 0.05 level of significance for local recurrence (0 per 228 versus 2 per 154; 1.3 percent) or survival. While narrower margins of resection for thinner, low-risk stage I malignant melanomas appear safe, the exact minimum margin of resection needed to satisfy both oncologic and cosmetic considerations, whether 1 or 2 cm, will need to be determined by a large prospective, randomized study.     

Distribution of planktonic ciliates in highly coloured subtropical lakes: comparison with clearwater ciliate communities and the contribution of myxotrophic taxa to total autotrophic biomass

SUMMARY 1. The planktonic ciliate communities of eleven organically coloured north and central Florida lakes representing a variety of trophic conditions were examined during 1979–80. The total abundance and biomass of ciliates were not significantly different from comparable clearwater lakes and only minor taxonomic replacements were noted at the order level.
2. Timing of population peaks of oligotrophic lakes was dissimilar to clearwater lakes of the same trophic state, but seasonality in meso-trophic and eutrophic lakes resembled patterns described for comparable clearwater lakes.
3. Various ciliate components were strongly correlated with chlorophyll a concentrations, but only moderately correlated to dominant phytoplankton groups. No significant correlations were found between ciliate components and bacterial abundance.
4. Myxotrophic taxa numerically dominated oligotrophic systems, particularly during midsummer, and accounted for a large percentage of the total ciliate biomass. Estimates of the ciliate contribution to total autotrophic biomass indicate that these zoochlorellae-bearing protozoa may account for much of the autotrophic biomass during midsummer periods in coloured lakes, and thus may lead to an overestimation of phytoplankton standing crops available to zooplankton grazers if chlorophyll a is used as a surrogate measure of algal biomass.